Such valve devices are used to control the pressure of hydraulic actuators, for example, in control systems for automatic transmissions, or to control the pressure in an actuator chamber of a variable oil pump of an oil circuit for the lubrication of an internal combustion engine of a motor vehicle. A ring of a feed chamber, on which the rotor of a vane pump or a gear pump runs, is here shifted or twisted via the pressure in the control chamber, whereby the displacement volume is changed.
The pressure control valves used for these purposes are designed as multi-port valves, for example, by which the pump control chamber can either be relieved via the oil sump or be charged with additional pressure from the feed pressure of the oil pump.
Such a system for controlling the pressure in two control chambers of an oil pump using a solenoid valve is described, for example, in DE 11 2008 000 978 T5. The differential pressure between the two control chambers is here changed as a function of the feed pressure and the position of the valve tappet of the solenoid valve.
A multi-port solenoid valve is described in DE 103 30 779 A1 which comprises an electromagnetically actuable valve member controlling a flow cross section between a control port and an outlet by translational movement of an armature of the solenoid that is connected with the valve member and is loaded by a spring element. The valve also has a spring-loaded ball as a second closing member between an inlet port and the control port so that the control port can be supplied with pressure from the inlet port due to the fact that a protrusion of the valve member, which extends towards the ball, pushes the ball from its valve seat due to the force of the spring element between the armature and the core. The armature is pulled by actuating the solenoid, and the valve element is thereby pulled towards the armature, whereby the passage from the control port to the outlet port is cleared, and the ball closes the connection of the control port to the inlet port.
DE 10 2010 025 171 A1 describes a fluid pressure switching valve which also comprises an outlet port closer to the actuator and an inlet port remote from the actuator, as well as a control port of a variable oil pump arranged between the inlet port and the outlet port. This valve is not pressure compensated, however, since, while a fluidic connection between the inlet port and an actuator chamber between the armature and the core may be formed by a bore in the armature and in the valve tappet, the force application surfaces are realized with different dimensions. In this valve, the connection between the inlet port and the control port is moreover interrupted in the non-energized state. This means that the oil pump must be designed so that, when the control pressure rises, a decrease in the displacement volume of the pump must follow so as to be able to ensure a sufficient lubrication of an internal combustion engine in the event of a dysfunctional solenoid.
Both valves thus have a drawback in that, due to the absence of pressure compensation, they are dependent on the magnitude of the prevailing feed pressure for the necessary armature opening force. The return spring and the solenoid must thus be adapted to existing forces. Known solenoid valves therefore require very great actuating forces when used in other pressure ranges so that other solenoids must be used.